Hard- and Soft-Switched
Technical Lecture Session
DC-DC Converter Applications
DC-DC converter, EMI reduction, Input Ripple Suppression, Automotive
This paper presents an isolated gate driver and double-NMOS-based Kappa switching DC-DC converter which has both continuous input and output currents. With two inductors isolating both input and ground, minimized di/dt hot loop formed by flying capacitor and two power switches, both Kappa buck and Kappa boost converters can be configured to achieve respective step-down and step-up voltage conversions. The Kappa buck converter, with one inductor connecting to input, has a continuous input current which can significantly reduce the input ripple, mitigate EMI noise and eliminate the bulky input EMI filters required by the conventional buck converter. Meanwhile, the load current is distributed between two inductors to reduce inductor DCR loss, but only two switches are required compared to conventional two-phase buck converter. A Kappa buck converter with isolated gate driver is implemented to achieve a DC-DC conversion from 48V to 5V. Compared to a conventional buck converter with same passive component values and operating conditions, this Kappa converter has an input ripple of 14mV, achieving 86.7% input ripple suppression and 16dB peak EMI noise reduction.